A suspension fork for bicycles and motorcycles includes a reversed arch that is integrally connected between the upper ends of the outer telescopic leg sections of the fork. The reversed arch is inclined rearwardly of the fork, thereby to reduce the possibility of interference with the brake means of the cycle.
Front suspension forks for cycles such as bicycles and in motorcycles are well known in the prior art, as evidenced by the patents to Turner U.S. Pat. Nos. Des. 401,537 and 4,971,344, and Boyer, et al., U.S. Pat. No. 5,653,007. In such known suspension forks, the vertical leg portions of the fork comprise a pair of telescopic tubular sections the inner ones of which are connected at their upper ends with a horizontal crown that is connected intermediate its ends with the handlebar steerer rod or shaft. The outer fork sections (i.e., the xe2x80x9cslidersxe2x80x9d) are connected at their upper ends by a transversely extending arch, thereby to define a unitary slider component the lower ends of which are connected with opposite ends of the wheel axle. Shock absorber means are provided that include a compression spring that biases the sections apart and damper means are provided for dampening fork vibratons.
As shown by the aforementioned Turner utility patent, the fork sliders initially consisted of three or more pieces bolted together. The arch was the piece that tied the right and left sliders together so they moved in tandem. Early technology and manufacturing techniques yielded forks that were very flexible. To fight the flex problem and reduce hardware proliferation, the cantilever pivot bolts were also used to anchor the arch to the sliders. Since cantilever rim brakes are generally mounted on the front of the fork, the arch was also mounted on the front. As fork designs and technology progressed, the sliders became increasingly integrated. Eventually, as shown by the Boyer et al., patent, the sliders were bonded instead of bolted together, thereby to define a unitary slider component. This relieved the arch of its previous duties, but it remained on the front nonetheless. Finally, as shown by the Turner design patent, the sliders were cast as one-piece.
In these known suspension forks, the wheel brake operating means are generally mounted forwardly of the suspension fork, and the arch similarly extends between the forward portions of the upper ends of the outer concentrically arranged fork section. Consequently, these forks have the disadvantage that the arch connection between the fork leg outer sections cannot be optimized for strength without interfering with the brake operation and design of the brake means.
Pace Cycles Limited of York, England, has proposed suspension forks that include arches that are clamped or bolted to the front and/or rear surfaces of the outer tubular sections of the suspension fork. In the Pace RC-35 suspension fork that was offered for sale in 1993, a separate arch component was clamped onto the rear side of the fork, as were the brake means. In the Pace forks, the arches and the brake means were mounted on the same side of the fork, whereby the arches interfere to some extent with the operation of the brake means, since as with other designs, the brake means are coincident with the arch.
The present invention was developed to avoid the above and other drawbacks of the suspension forks of the prior art. During its development of its one-piece cast sliders, Applicant discovered that the greatest increase in stiffness resulted when the arch was xe2x80x98wrappedxe2x80x99 and thickened around the inside of the sliders, but the amount of wrap and the thickness of the possible material was limited. This was due to the fact that the additional wrap meant and material greater mass, and this greater mass interfered with the operation of the cantilever brakes. A reduced opening made wheel installation and removal of the wheel difficult or impossible. In the end, the state-of-the-art sliders were a compromise between optimal stiffness on the one hand, and ease of wheel installation and removal on the other hand.
Accordingly a primary object of the present invention is to provide a suspension fork in which the arch means for connecting the fork leg outer section are inclined rearwardly at an acute angle relative to the vertical plane of the fork. In this manner, the reversely inclined arch does not interfere with the operation of the brake means arranged forwardly or rearwardly of the fork.
According to another feature of the invention, in order to obtain a higher stiffness to weight ratio, each of the lower ends of the inverted U-shaped arch includes a stiffening wrap mass that extends between the lower leg portions of the arch and the adjacent upper portions of the respective outer fork sections, without negatively affecting operation of the brake means. The resulting increase of the torsional stiffness of the sliders reduces binding of the sliders relative to the stanchions over which they slide during the suspension movement, thereby offering a smoother ride. The arch may be nearly xc2xd inch shorter owing to its relative position behind the axle of the wheel, whereby the shorter arch is stiffer and lighter as well.
According to a further object of the invention as applied to a fork using cantilevered rim brake means, the brake posts extend forwardly of the fork and are arranged off-center in the direction of each other. The brake posts are reduced in height, since the brake arms no longer must clear a front-mounted arch. This permits the brakes to be arranged closer to the centerline of the fork, thereby decreasing their twisting leverage over the outer fork sections. This results in cantilever bracing with improved modulation and power.
A further object of the invention is to provide a suspension fork for use with disc brake means wherein the slider member includes a rearwardly inclined arch connected between the upper ends of the lower sections, and disc brake mounting posts arranged at the lower rear end of one of the lower leg sections, thereby to provide a rigid slider unit.
According to another object of the invention, the rearwardly inclined reversed arch shields the seals of the fork against dirt and debris produced by rotation of the associated tire. The reversed arch construction affords improved slider torsional stiffness, reduction in slider weight, and protection of the fork seals.